<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>TEST</title>
  <style>
    /* 基本的 CSS 重置 */
    *,
    *::before,
    *::after {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    html,
    body,
    #app {
      width: 100%;
      height: 100%;
      font-size: 16px;
      font-family: 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, 'Noto Sans', sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol', 'Noto Color Emoji';
      -webkit-font-smoothing: antialiased;
      -moz-osx-font-smoothing: grayscale;
    }
  </style>
</head>

<body>
  <div id="app">A</div>
</body>

</html>